I would like to run three low-voltage cables from my entertainment center through an old plaster wall, down (1-3 feet) through the sill plate, and into the crawlspace.

The cables are Ethernet, coaxial-something (for a roof mounted UHF/VHF TV antenna which we haven't installed yet) and speaker wire.

Will this gang box will be too crowded? Is there an easy way to give me more space inside the gang box, or to deal with the thick coaxial cable?

I might want to run additional wires into this box later, such as phone cable for our DSL connection, or maybe an HDMI connection to another room (but this is a fantasy). Since I have existing wires in the box, will routing new cables through this box and through be a problem?

I have a raised crawlspace (4 feet high or more). I need to get the cables from behind the wall into the crawlspace. It looks like many people drill a hole through the sill plate and then route the cables through the hole. Is this recommended, or does it cause any structural issues? I would be drilling the hole from the crawlspace up into the wall. From the room above, I would then need to cut a hole through the plaster. Is there a way to make these two holes line up?

3 Answers
3

You've got a lot of different questions, so I'll try to answer the ones I can:

Coax sucks because of the necessary bend. You're better off going with a backless box like the one you linked to, because it makes running cables so much easier. (if you have a second person, have them push the cables up from below (or a straightened coat hanger or other wire to act as a needle, if the bundle of cables is too floppy), and then snag it from the hole with a wire bent into a hook) ... which you can't do as easily if you mount a box with little punchouts. Also, you then don't have to worry about crowding the box, etc.

It's easier to run lots of cables at once. What what you're planning already, I'd likely run an extra cat5e/cat6 cable, and then get an HDMI-over-twisted-pair (aka HDMI-over-cat5) extender if you wanted to go that route, or re-terminate it for RJ11 if you wanted to change it over to phone.

I don't know of any other way to get cables/pipes through the sill other than drilling, and it's allowed for plumbing, electrical, etc, so long as you then spray foam the holes afterwards (at least, it's required in my area, might not be in yours).

You only need to line up well enough to get it in the same bay, so you have a ~14.5" target. I cut the hole for the box first, then check to verify the location of the studs (I don't use hardware that requires me to attach to a stud, so I just have to make sure to miss it when cutting my hole), then measure off of some reference point that I'll be able to find down below. (electrical runs, walls, etc.) If nothing else, you can use plumbing or electrical for identifying where the walls are from below.

To avoid humidity issues, use spray foam to seal around the cables. (see #3). It may even be required by code in your area.

If your "plaster" walls are lath-and-plaster, you'll probably find it easier to mount the box horizontally because you'll have to cut through fewer lath to make the opening (you might get away with just cutting one). A previous owner of my house did this for some receptacles; IMO they look odd, but if your box will be behind an entertainment center, it doesn't make any difference.

Write a number on each box of cable. Put the same number of stripes on the end of each corresponding cable.

Pick a location for the outlet. Make sure it's not over a stud. Cut a hole for a mounting bracket. Use the bracket as a guide, and a level to make it look nice.

Chuck an insulation hanger wire in a drill, like a drill bit. Drill a tiny hole in the floor, right up against the baseboard (or behind the baseboard). Unchuck the wire, leave the hanger in the floor for now.

Have an assistant pluck the hanger from above, while I crawl underneath with a drill, fish tape, electrical tape, staple gun, and flashlight. I follow the sound of the plucked wire hanger.

Drill a hole through the sill plate, using the hanger as a reference, e.g. "2 inches towards the front door".

Push fish tape up from below.

Have assistant grab the fish tape & attach the cables.

I pull the cables down with the fish, and lead them back to the home run point. Assistant helps the cables move freely from the other end. Avoid having too much slack when you're done.

Working from the home run point back, wrap the cables in electrical tape every 1-2 feet. Staple one cable (COAX if you have one in the bundle, because it's tougher) to the joists.

Have the assistant pull up the excess slack. Leaving at least 2 feet of extra cable hanging out of the wall, mark each cable with the correct number of stripes. Cut with about a foot extra beyond the stripes, so you can still see them when you strip the housing later.